Low-cost, high-precision, single-frequency GPS–BDS RTK positioning

The integration of the Chinese BDS with other systems, such as the American GPS, makes precise RTK positioning possible with low-cost receivers. We investigate the performance of low-cost ublox receivers, which cost a few hundred USDs, while making use of L1 GPS + B1 BDS data in Dunedin, New Zealand. Comparisons will be made to L1 + L2 GPS and survey-grade receivers which cost several thousand USDs. The least-squares variance component estimation procedure is used to determine the code and phase variances and covariances of the receivers and thus formulate a realistic stochastic model. Otherwise, the ambiguity resolution and hence positioning performance would deteriorate. For the same reasons, the existence of receiver-induced time correlation is also investigated. The low-cost RTK performance is then evaluated by formal and empirical ambiguity success rates and positioning precisions. It will be shown that the code and phase precision of the low-cost receivers can be significantly improved by using survey-grade antennas, since they have better signal reception and multipath suppression abilities in comparison with low-cost patch antennas. It will also be demonstrated that the low-cost receivers can achieve competitive ambiguity resolution and positioning performance to survey-grade dual-frequency GPS receivers

Experiments on Long-term Geodetic Monitoring by Low-cost GNSS Receivers and GoGPS Positioning Engine

This paper describes experiments of GNSS-based monitoring by means of different models and brands of low-cost receivers. Single-frequency observations were processed by Open Source goGPS Positioning Engine, in relative positioning mode with respect to a virtual reference station and three physical permanent stations. The experiments were carried out in Osaka, Japan and the results here described cover a timespan of eight months. The daily solutions show standard deviations ranging from about 1mm to 1cm, mainly depending on the base station observations quality

Ionospheric biases correction for coordinates derived from GPS single point positioning

Most GPS users employ low cost receivers. These receivers do not allow users to record the pseudorange that they observe, but the computed coordinates. This work presents an original and simple method to correct ionospheric biases introduced in GPS signals. The originality of this method is based on the fact that no pseudorange is needed to correct the biases, only the calculated coordinates are used. This distinguishes this method from other classic alternatives. This paper evaluates the efficiency of the method with the use of real data.Facultad de Ciencias Astronómicas y Geofísica

Consensus-Based Distributed Filtering for GNSS

Kalman filtering in its distributed information form is reviewed and applied to a network of receivers tracking Global Navigation Satellite Systems (GNSS). We show, by employing consensus-based data-fusion rules between GNSS receivers, how the consensus-based Kalman filter (CKF) of individual receivers can deliver GNSS parameter solutions that have a comparable precision performance as their network-derived, fusion center dependent counterparts. This is relevant as in the near future the proliferation of low-cost receivers will give rise to a significant increase in the number of GNSS users. With the CKF or other distributed filtering techniques, GNSS users can therefore achieve high-precision solutions without the need of relying on a centralized computing center

Building an end user focused THz based ultra high bandwidth wireless access network: The TERAPOD approach

The TERAPOD project aims to investigate and demonstrate the feasibility of ultra high bandwidth wireless access networks operating in the Terahertz (THz) band. The proposed TERAPOD THz communication system will be developed, driven by end user usage scenario requirements and will be demonstrated within a first adopter operational setting of a Data Centre. In this article, we define the full communications stack approach that will be taken in TERAPOD, highlighting the specific challenges and aimed innovations that are targeted

Single-Photon Avalanche Diodes in CMOS Technologies for Optical Communications

As optical communications may soon supplement Wi-Fi technologies, a concept known as visible light communications (VLC), low-cost receivers must provide extreme sensitivity to alleviate attenuation factors and overall power usage within communications link budgets. We present circuits with an advantage over conventional optical receivers, in that gain can be applied within the photodiode thus reducing the need for amplification circuits. To achieve this, single-photon avalanche diodes (SPADs) can be implemented in complementary metal-oxide-semiconductor (CMOS) technologies and have already been investigated in several topologies for VLC. The digital nature of SPADs removes the design effort used for low-noise, high-gain but high-bandwidth analogue circuits. We therefore present one of these circuit topologies, along with some common design and performance metrics. SPAD receivers are however not yet mature prompting research to take low-level parameters up to the communications level

A combined receiver front-end for Bluetooth and HiperLAN/2

A Software Defined Radio is a radio receiver that is reconfigurable by software. This reconfigurability leads to flexibility that can be used to offer more functionality to the user. Also, because common reconfigurable hardware can be used for very diverse radio interfaces, production and logistics can be faster and cheaper. In our Software Defined Radio project we aim at a receiver that is able to receive signals of any contemporary or future radio standard. However, because we need tangible specifications in order to design, we have chosen to implement a combination of two rather different standards: Bluetooth and HiperLAN/2. Both the analogue and the digital/software parts are included in the design. A CMOS integrated wideband analogue front-end containing a low noise amplifier, downconversion mixers and filters has been designed. This front-end\ud is connected to a PCB that contains two analogue-to-digital convertors and a sample rate convertor (SRC). The output of this board is connected to a standard PC through a digital I/O board with PCI bus. Software on this PC performs the demodulation.\ud We conclude that an analog wide-band front-end with a flexible SRC combined with appropriate software on an inherently flexible PC forms a promising architecture for Software Defined Radio

High precision GPS guidance of mobile robots

The use of GPS for guidance of mobile robots has been reported as achieved in a number of useful proximate scenarios such as stevadoring, formation movement or search and agricultural positioning. Standard DGPS can be used to get an accuracy of under one metre sometimes leaving fine motor adjustments by humans to complete a task. Pay a lot more, and the precision improves but the cost is high in any commercial terms for the mass market. We report high precision GPS-guided movement based on the use of readily available low-cost receivers. Accuracies of better than 5 cms maintained over minutes have been demonstrated and are being improved upon. The guidance algorithms were adjusted to allow for the retention of orientation when approaching close to a destination. The introduction of the Galileo system will improve the efficacy and usefulness of this method as we move from 24 to 30 satellites